There is an ongoing need for solid state circuits adapted to operate at higher and higher frequencies, including microwave frequencies. As used herein, the term “microwave” is intended to refer to frequencies at or above about 800 mega-Hertz. Various transistor structures have been created that are capable of providing gain in such frequency ranges. A LDMOS (Lateral Diffused Metal Oxide Semiconductor) transistor is an example of such a transistor structure.
A Monolithic Microwave Integrated Circuit (MMIC) may include a substrate with one or more arrays of LDMOS transistor structures, each array providing a stage of an amplifying circuit. The MMIC may further include passive components such as capacitors, inductors and resistors arranged on the surface of the substrate to complete the circuit. At high frequencies parasitic coupling between the components of the circuit can limit performance.
Therefore, further improvements to reduce parasitic coupling in semiconductor devices for use at higher frequencies, such as MMICs, are desirable.